I found this user research study to be quite interesting. The key nugget:

"However, the key UX advantage of WeChat is not that it grew out of a chat service; it’s the integrated user experience. Each individual service is fine, but not necessarily better than those offered by other companies. In fact, our user testing of WeChat revealed many usability problems in various areas. What’s superior is how these services play together and reinforce each other. Most importantly, these benefits are not the result of a superior, simple conversational UI; instead, they are often provided through a simplified graphical user interface (GUI)."

In other words, while the western world buzzes that WeChat is huge because of the messaging interface, it's pretty clear it has more to do with the streamlining of elements such as payments and mobile websites. In that regard, WeChat is almost more akin to America Online -- the old, dial-up variety -- than to say, Facebook Messenger and the like (though they're getting halfway there with payments).

(Aside: I know someone sent me this link and I can't find where that was now -- if you're reading this, feel free to shoot me a note for full credit.)